Oxytocin is a nine-amino acid peptide (Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly-NH₂) with an internal disulfide bridge. It is synthesized as a larger precursor in hypothalamic neurons and packaged into vesicles transported to the posterior pituitary for release into circulation, or released locally within the brain as a neuromodulator.

The peptide's role as a 'social bonding hormone' has driven extensive research into its effects on trust, prosocial behavior, stress reduction, and anxiety. Beyond neuroscience, oxytocin receptors are expressed in muscle, fat, bone, and cardiovascular tissue — revealing metabolic, anabolic, and cardiovascular functions. Research has shown it reduces cortisol, promotes muscle stem cell function, and may have bone-protective effects.